Go: undefined function in same package [duplicate]

I've started Go and am trying to follow this tutorial. Everything builds correct but as I try to run it, I get the error that makeRouter() could not be found.

I had a look at some other questions, like this one, and checked the docs, but I couldn't find out whats wrong with my setup.

My folder structure:

.../wattagebazooka/
  |- wattagebazooka.go
  |- router.go
  |- handler.go

Code

package main

import (
    "database/sql"
    "fmt"
    "log"
    "net/http"
    "runtime"

    _ "github.com/lib/pq"
)

// init sets runtime settings.
func init() {
    // Verbose logging with file name and line number
    log.SetFlags(log.Lshortfile)

    // Use all CPU cores
    runtime.GOMAXPROCS(runtime.NumCPU())
}

var db *sql.DB

func main() {
    db = openDB()
    defer db.Close()

    r := makeRouter()
    http.Handle("/", r)
}

func openDB() *sql.DB {
    dbName := "wattagebazooka"

    db, err := sql.Open("postgres", fmt.Sprintf("user=ts password= dbname=%s host=127.0.0.1", dbName))
    if err != nil {
        log.Fatalf("Error connecting to the %s database as user ts: %v", dbName, err)
    }

    return db
}

package main

import "github.com/gorilla/mux"

func makeRouter() *mux.Router {
    r := mux.NewRouter()
    r.HandleFunc("/user/me", wrapHandler(userHandler)).Methods("GET")
    r.HandleFunc("/text", wrapHandler(textHandler)).Methods("POST")
    r.HandleFunc("/text/{hash}", wrapHandler(textHashHandler)).Methods("GET")
    return r
}

Build

> Environment:
>   GOROOT=/usr/local/go
>   GOPATH=/Users/ts/Developments/gocode
> Directory: /Users/ts/Developments/gocode/src/github.com/wattagebazooka/wattagebazooka
> Command: /usr/local/go/bin/go build -v
> Output:
github.com/wattagebazooka/wattagebazooka
> Elapsed: 0.708s
> Result: Success

Run

> Environment:
>   GOROOT=/usr/local/go
>   GOPATH=/Users/ts/Developments/gocode
> Directory: /Users/ts/Developments/gocode/src/github.com/wattagebazooka/wattagebazooka
> Command: /usr/local/go/bin/go run -v /Users/ts/Developments/gocode/src/github.com/wattagebazooka/wattagebazooka/wattagebazooka.go
> Output:
command-line-arguments
# command-line-arguments
./wattagebazooka.go:28:7: undefined: makeRouter
> Elapsed: 0.244s
> Result: Error